A field guide to mesozoic birds and other winged dinosaurs

Heavy Tail Feather No scientific name (specimen number BPM 0001)
Time: 124.5 Ma ago Location: Liaoning, China Habitat: Lower Yixian Formation (see
above) Size: WS 85cm (2.8ft); BL 75cm (2.5ft); TL unknown Features: Head long & rectangular
w/ robust, blunt snout. Nasal opening relatively large compared to other caudipterids.
Teeth restricted to tip of upper jaw; lower jaw toothless. Front two teeth large.
Wings relatively small. Minor digit highly reduced, lacking a claw & probably fused to
major digit via soft tissue. Alular claw slightly larger than major claw. Legs long. Tail very
short. Biology: While details of the feathers are not well preserved in this species, it is
clearly different from other caudipterids in the more rectangular shape of the skull, which
is probably a primitive characteristic.
Yixian Similar Caudipter Similicaudipteryx yixianensis
Time: 124.5 - 120 Ma ago Location: Liaoning, China Habitat: Yixian (see above) and
Jiufotang Formation, cool, swampy marshlands. Size: WS ~ 90cm (3ft); BL 1m (3.3ft); TL
~1.3m (4.3ft) Features: Head high & rounded. Wings very large in subadults & adults.
Wings in juveniles much smaller & lacking secondary remiges. Tail frond extremely large
relative to body size & extending to the tail base in adults, unlike other known caenagnathiformes.
Yixian specimens may represent a distinct species. Biology: Adult (Jiufotang)
specimen possess fused, pygostyle-like tail vertebrae, indicating that the tail frond may
have become even larger in mature individuals. The wings & tail frond were relatively
small in juveniles, similar in proportion to Caudipteryx zoui. In immature specimens, the
rectrices were longer than the primary remiges, & secondary remiges were absent. This
indicates that the tail frond grew large first, & that the wings developed more slowly, likely
being less important to juveniles. In adults, the wings & tail frond were more equal in
size, but the rectrical frond was still larger than the wings, much larger than any other
caudipterid. The significant size & late development of the wings & tail indicate that these
structures were primarily used for display in this species.
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